Extreme hurricane flooding in the northeastern United States, which once occurred once every 100 years, could become an annual occurrence by the end of this century, a new study has found.
The researchers wanted to predict how changes in hurricane behavior (which are expected to become more frequent and intense) and rising sea levels due to climate change would change the region’s flood risk in coming decades.
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The researchers also adjusted the model to take into account the angle at which the storm hits the coast. Most hurricanes that impact the Northeast move parallel to the coast, but some, like Hurricane Sandy in 2012, hit head-on and can cause more damage. “It’s extreme but rare,” Begmohammadi said.
The model predicts that extreme flooding events may become more frequent due to rising sea levels and changes in storm characteristics. Historical 100-year coastal floods could occur every year by the end of this century, while historic 500-year floods could occur every 1 to 60 years under moderate carbon emissions scenarios and every 1 to 20 years under high emissions scenarios. In northern regions such as Connecticut and New York, sea level rise may be the main driver of increased flood risk, while changes in storms are less important. Further south, in areas such as New Jersey and Virginia, both factors can significantly contribute to increased flood risk.
The findings were published in the journal Earth’s Future on November 7th.
Geoff Olerhead, a coastal geomorphologist at Mount Allison University in Sackville, Canada, said the study highlights how scientific uncertainty is an unimportant variable in predicting future climate risks. Ollerhead, who was not involved in the study, told Live Science that much of the variation in the models comes from “social uncertainty”: not knowing what emissions path the world will follow. “We don’t know what people will do,” he said, referring to how political leaders will respond to the climate crisis. “That’s the biggest uncertainty.”
The new study focused on the strength and frequency of hurricanes. For areas farther north on the coast, the effects of rising sea levels mean even stronger storms will matter little because even small storms can cause major flooding, Olerhead said. Therefore, as sea levels continue to rise, the impact of each storm increases, even if the frequency and intensity of the storms are about the same.
Hurricane Fiona, which hit the Orrhead region of Atlantic Canada in 2022, had storm surges of nearly 6.5 feet (2 meters). But if sea levels rise by 1 meter over the next 50 years or so, a storm half that strong could cause similar damage. “It’s going to take a smaller event to fill the backyard with water,” he says. “And they may happen every few years.”
To prepare for this new reality, people living near the coast will need to adapt to more frequent flooding. The best defense, Ollerhead said, is to move back to higher ground away from the coast. However, not all communities have the desire or ability to do so, making it important to update building codes to account for changing circumstances.
Begmohammadi said, “Resilience designers are designing based on what happened 100 years ago, but they are not designing with future changes in mind.” “What happened in the past 100 years is not the same as what will happen in the future.”
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